Image forming apparatus and apparatus for correcting difference in oscillation speed among oscillating devices

Abstract

An image forming apparatus includes a device-information storage unit configured to store a scanning frequency of an oscillating device; an image storage unit configured to store image data used for image formation; an image processing unit configured to perform an enlargement or reduction, in a direction orthogonal to a direction of the scanning of the laser beam and in accordance with a given parameter, on the image data stored in the image storage unit; a setting unit configured to calculate the parameter from the scanning frequency stored in the device-information storage unit and a predetermined reference frequency and configured to provide the parameter to the image processing unit; and a driving unit configured to drive a laser beam device according to the image data processed by the image processing unit.

1. An image forming apparatus comprising:
 an oscillating device configured to oscillate at a natural frequency; 
 a laser beam device configured to emit a laser beam; 
 a photoconductive drum, the oscillating device configured to scan the laser beam from the laser beam device across the photoconductive drum; 
 a device-information storage unit configured to store a scanning frequency of the oscillating device; 
 an image storage unit configured to store image data used for image formation; 
 an image processing unit configured to perform an enlargement or reduction, in a direction orthogonal to a direction of the scanning of the laser beam and in accordance with a parameter, on the image data stored in the image storage unit; 
 a setting unit configured to calculate the parameter from the scanning frequency stored in the device-information storage unit and a predetermined reference frequency and configured to set the parameter in the image processing unit; and 
 a driving unit configured to drive the laser beam device according to the image data processed by the image processing unit. 
 
     
     
       2. The image forming apparatus according to  claim 1 ,
 wherein the parameter is a difference between a sub-scanning width corresponding to the scanning frequency stored in the device-information storage unit and a sub-scanning width corresponding to the predetermined reference frequency. 
 
     
     
       3. The image forming apparatus according to  claim 1 ,
 wherein the parameter is a ratio of the scanning frequency stored in the device-information storage unit to the predetermined reference frequency. 
 
     
     
       4. The image forming apparatus according to  claim 1 ,
 wherein the image processing unit performs an overlapping interpolation process of a line image signal during the enlargement and performs a decimation process of a line image signal during the reduction. 
 
     
     
       5. The image forming apparatus according to  claim 1 ,
 wherein the image processing unit performs the enlargement or reduction by linear interpolation between adjacent line signals. 
 
     
     
       6. The image forming apparatus according to  claim 1 ,
 wherein the image forming apparatus is a color image forming apparatus that uses a plurality of coloring materials to form a color image, 
 wherein the image forming apparatus has a plurality of such oscillating device, the plurality including an oscillating device corresponding to a black coloring material, and 
 wherein the setting unit uses the frequency of the oscillating device corresponding to the black coloring material as the predetermined reference frequency. 
 
     
     
       7. The image forming apparatus according to  claim 1 ,
 wherein the image forming apparatus is a color image forming apparatus that uses a plurality of coloring materials to form a color image, 
 wherein the image forming apparatus has a plurality of such oscillating device, the plurality including an oscillating device closest to a second reference frequency, and 
 wherein the setting unit uses the frequency of the oscillating device closest to the second reference frequency as the predetermined reference frequency. 
 
     
     
       8. The image forming apparatus according to  claim 1 ,
 wherein the image forming apparatus is a color image forming apparatus that uses a plurality of coloring materials to form a color image, 
 wherein the image forming apparatus has a plurality of the oscillating device, and 
 wherein the setting unit uses the highest or lowest frequency among the frequencies of the oscillating devices as the predetermined reference frequency. 
 
     
     
       9. The image forming apparatus according to  claim 1 ,
 wherein the oscillating device is a MEMS scanner that cyclically oscillates about an axis. 
 
     
     
       10. The image forming apparatus according to  claim 1 ,
 wherein the image processing unit performs the enlargement or reduction in response to the given parameter exceeding a predetermined range. 
 
     
     
       11. The image forming apparatus according to  claim 1 , further comprising a measuring unit configured to measure the frequency of the oscillating device at a predetermined timing and store the frequency in the device-information storage unit. 
     
     
       12. A method for forming an image using an image forming apparatus, the image forming apparatus comprising: an oscillating device configured to oscillate at a natural frequency; a laser beam device configured to emit a laser beam; a photoconductive drum, the oscillating device configured to scan the laser beam from the laser beam device across the photoconductive drum; a device-information storage unit; an image storage unit; an image processing unit; a setting unit, and a driving unit; the method comprising:
 storing a scanning frequency of the oscillating device in the device-information storage unit; 
 storing image data used for image formation in the image storage unit; 
 using the image processing unit to perform an enlargement or reduction, in a direction orthogonal to a direction of the scanning of the laser beam and in accordance with a parameter, on the image data stored in the image storage unit; 
 using the setting unit to calculate the parameter from the scanning frequency stored in the device-information storage unit and a predetermined reference frequency and configured to set the parameter in the image processing unit; and 
 using the driving unit to drive the laser beam device according to the image data processed by the image processing unit. 
 
     
     
       13. A non-transitory computer-readable storage medium that stores a program of computer-executable code executable by a computer to form an image using an image forming apparatus, the image forming apparatus comprising: an oscillating device configured to oscillate at a natural frequency; a laser beam device configured to emit a laser beam; a photoconductive drum, the oscillating device configured to scan the laser beam from the laser beam device across the photoconductive drum; a device-information storage unit; and an image storage unit; the program of computer-executable code comprising:
 computer-executable code for storing a scanning frequency of the oscillating device in the device-information storage unit; 
 computer-executable code for storing image data used for image formation in the image storage unit; 
 computer-executable image processing code for performing an enlargement or reduction, in a direction orthogonal to a direction of the scanning of the laser beam and in accordance with a parameter, on the image data stored in the image storage unit; 
 computer-executable code for calculating the parameter from the scanning frequency stored in the device-information storage unit and a predetermined reference frequency and configured to set the parameter for use by the computer-executable image processing code; and 
 computer-executable code for driving the laser beam device according to the image data processed by the computer-executable image processing code.